mybatis关系映射之一对多和多对一详解

/**
* 客户实体
*/
public class Person {

private String id;
private String name;
private String address;
private String tel;

private List<Order> orders;

@Override
public String toString() {
return "{id: " + id + ", name: " + name + ", address: " + address + ", tel: " + tel + "}";
}
}

/**
* 订单实体
*/
public class Order {

private String id;
private String number;
private int price;

private Person person;

@Override
public String toString() {
return "{id: " + id + ", number: " + number + ", price: " + price + "}";
}

}

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.zdp.domain.Person">

<resultMap type="Person" id="personBean">
<id column="personId" property="id"/>
<result column="personName" property="name"/>
<result column="personAddress" property="address"/>
<result column="personTel" property="tel"/>

<!-- 一对多的关系 -->
<!-- property: 指的是集合属性的值, ofType：指的是集合中元素的类型 -->
<collection property="orders" ofType="Order">
<id column="orderId" property="id"/>
<result column="orderNumber" property="number"/>
<result column="orderPrice" property="price"/>
</collection>
</resultMap>

<!-- 根据id查询Person, 关联将Orders查询出来 -->
<select id="selectPersonById" parameterType="string" resultMap="personBean">
select p.*, o.* from person p, orders o where p.personId  = o.pid and p.personId = #{id}
</select>

</mapper>

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.zdp.domain.Order">
<resultMap type="Order" id="orderBean">
<id column="orderId" property="id"/>
<result column="orderNumber" property="number"/>
<result column="orderPrice" property="price"/>

<!-- 多对一的关系 -->
<!-- property: 指的是属性的值, javaType：指的是属性的类型-->
<association property="person" javaType="Person">
<id column="personId" property="id"/>
<result column="personName" property="name"/>
<result column="personAddress" property="address"/>
<result column="personTel" property="tel"/>
</association>
</resultMap>

<!-- 根据id查询Order, 关联将Person查询出来 -->
<select id="selectOrderById" parameterType="string" resultMap="orderBean">
select p.*, o.* from person p, orders o where p.personId  = o.pid and o.orderId = #{id}
</select>

</mapper>